Evaluation of white coat hypertension in Chinese children : predictive factors and outcome

Abstract

Objectives Hypertension is increasingly found in children. 24 hour ambulatory blood pressure monitoring is now preferred to office blood pressure measurement for diagnosis and monitoring. Blood pressure of children tends to fluctuate widely throughout the day and night. A number of children suffer from a condition called white coat hypertension in which elevation of blood pressure is only transient and they usually have normal blood pressure on continuous monitoring. This condition is not totally benign. Some patients will evolve into hypertension over time. This retrospective case control study is to compare the demographic characteristics and blood investigations of these 2 groups namely white coat hypertension cases and a control group so as to identify factors predictive of white coat hypertension in a Chinese population to help allocate resources for timely diagnostic investigation.

Method 100 patients referred from primary health care units aged 6-18 year old for suspected hypertension based on raised office blood pressure measurements were recruited as cases in the white coat hypertension group and 100 age-matched patients as a control group. The factors studied included gender, body mass index, length of gestation, birth weight, family history of hypertension, positive past medical history, blood pressure at first presentation, blood pressure of ambulatory blood pressure monitoring, serum glucose, urate and cholesterol and triglyceride level. Univariate analysis was used to detect significant difference between the cases and the controls for continuous and categorized variables. Logistic regression was used to assess the independent associations of significant predictive factors of white coat hypertension. Correlations with the scatterplots for the relation of office systolic blood pressure and diastolic blood pressure with 24 hour ambulatory blood pressure monitoring within cases was done to see if there was any significant relations. The outcome of cases was also studied for the proportion which progressed into genuine hypertension.

Results Body mass index (BMI) was identified as a significant predictive factor in logistic regression with an odds ratio of 1.18 (95% CI = 1.11-1.25) with p-value <0.001. The correlation between 24 hour ambulatory blood pressure and office blood pressure measurement was not significant. None of the cases progressed into genuine hypertension upon follow up. Conclusion To conclude, this study showed that high BMI might be predictive of white coat hypertension in Chinese children in Hong Kong. This result could be act as a hypothesis for future research. Multi-centre prospective cohort studies might be of value in testing this factor together with factors which were shown to be significant in other studies. White coat hypertension is not always as benign as thought. Obesity is a condition which requires attention from patients, parents, paramedics and healthcare practitioners especially in primary healthcare settings and should be monitored more closely for the emergence of associated complications.